DESCRIPTION (Applicant's Description): Abnormal chromosome number (aneuploidy) has been observed in many human tumors but the mechanism by which cells become aneuploid is not known. Defective spindle function during anaphase is one possible mechanism. The broad objective of the research outlined in this proposal is to identify genes important during anaphase and use the combination of yeast genetics, molecular biology, biochemistry, in vivo and in vitro studies to investigate the mechanism of spindle elongation in S. cervisiae during anaphase B. Investigating this step in mitosis should yield useful information to help explain aspects of the pathophysiology of human cancers as well as potentially provide new targets for anticancer treatment. One anaphase specific gene, ASE1, has recently been identified in S. cerevisiae. The location of ASE1 at the mitotic midzone in late anaphase/telophase suggests it may be important for spindle elongation. The research of the applicant will focus on determining the microtubule binding properties of ASE1, identifying other genes required for anaphase using a genetic screen for genes that have overlapping function with ASE1, and developing an in vitro system in which spindle elongation is reconstituted, ultimately with purified components. Eventually, analogous human genes will be identified and their role in malignant transformation studied. The applicant's prior training includes both a rigorous basic science background as well as extensive clinical experience. This project was selected because it allows her to combine her interests in microtubule-based activities with her clinical interests in oncology. In addition, she will gain expertise in the powerful techniques of yeast genetics and molecular biology. This training will provide an ideal environment for her to develop into an independent investigator with the long-term goal of continued research focused on understanding the pathophysiology of human cancers.